Sensorless Air Compressor Motor Startup With Rotor Pre-Alignment
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Solution Overview
Problem
Existing sensorless control methods for air compressors in fuel cell systems face challenges in early driving stages, where the motor speed control response is delayed due to the lack of Hall sensors, leading to inefficient air supply and vehicle acceleration performance, and rotor alignment failures occur when the rotor is not aligned to the intended position.
Innovation Solution
A method for controlling a sensorless motor in air compressors involves determining the motor's stopped state using sensorless control logic, aligning the rotor to a predetermined position using a d-axis current, and applying phase currents to forcibly rotate the rotor to the alignment target position, thereby improving speed control response and preventing rotor alignment failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control method is used without Hall sensor, then device complexity is reduced, but speed control response is delayed
Solution Approach 1:
The patent applies preliminary action by performing rotor position alignment before motor startup. The controller aligns the rotor to a predetermined position using alignment currents (d-axis and q-axis currents) before actual motor operation begins. This preliminary positioning eliminates the need for Hall sensors during startup while ensuring accurate initial rotor position, thereby resolving the contradiction between simplified device structure and improved speed control response.
2Device complexity
If rotor is not aligned to intended position, then device complexity is reduced, but rotor alignment failures occur
Solution Approach 1:
The controller performs preliminary rotor alignment by applying specific currents (d-axis alignment current and q-axis alignment current) to position the rotor at a predetermined angle before motor operation. This preliminary action ensures reliable rotor alignment without requiring additional alignment sensors or complex mechanisms, thus maintaining device simplicity while improving alignment reliability.
Solution Approach 2:
The patent implements feedback control during the alignment process. The controller continuously monitors the rotor position and adjusts the alignment currents accordingly to ensure the rotor reaches the intended position. This feedback mechanism guarantees accurate rotor alignment while keeping the overall system structure simple, resolving the contradiction between device complexity and alignment reliability.
3Device complexity
If open-loop control is performed for several hundreds of ms, then motor can be driven without Hall sensor, but control response is delayed
Solution Approach 1:
The patent eliminates the need for lengthy open-loop control by performing rotor alignment as a preliminary action before motor startup. The controller aligns the rotor to the exact predetermined position using calculated alignment currents, then immediately transitions to closed-loop control. This approach removes the several hundred milliseconds of open-loop control delay while maintaining sensorless operation, thus resolving the contradiction between device simplicity and response time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances speed control response and air supply efficiency, reduces unnecessary torque application, and improves vehicle acceleration performance by accurately aligning the rotor, thus overcoming the limitations of traditional sensorless control methods.
Implementation Method 1
controlling a position of the rotor to change from an alignment start position to an alignment target position
Implementation Method 2
controlling a phase of a phase current applied to the motor so that the position of the rotor changes from the alignment start position to the alignment target position
Data Source
AI summary
Provided is a method of controlling a sensorless motor for an air compressor. The method controls early driving of a sensorless motor for an air compressor, overcomes related-art problems, and improves control response. A position of a rotor of the motor, finally estimated by a sensorless control logic at a point in time at which the motor is determined to be in the stopped state, is determined to be an alignment target position. An alignment start position is determined from the alignment target position in accordance with a predetermined alignment offset angle. The position of the rotor of the motor is controlled to change from the determined alignment start position to the alignment target position.